Projection Optical Device And Exposure Apparatus

ABSTRACT

A projection optical device includes a projection optical system which projects an image of a pattern, a support device having a flexible structure to support the projection optical system, and a positioning device having an actuator to position the projection optical system. The projection optical device can include a frame to which one end of the flexible structure is attached. The projection optical system may hang from the frame via the support device, or it may be supported from below by the support device. A projection optical device also can include a liquid supply which supplies a temperature-controlled liquid to a side surface of a projection optical system utilizing gravity to cause the temperature-controlled liquid to flow along the side surface of the projection optical system.

This application claims the benefit of U.S. Provisional Application No.60/614,426, filed Sep. 30, 2004. The disclosure of U.S. ProvisionalApplication No. 60/614,426 is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to a projection optical device provided with aprojection optical system which projects an image of a predeterminedpattern, and to an exposure apparatus which is used in order to transfera pattern of a mask onto a substrate in order to manufacture variousdevices such as, for example, a semiconductor device, a liquid crystaldisplay, etc.

2. Description of Related Art

In a lithography process, which is one process used to manufacture asemiconductor device, an exposure apparatus is used in order to transferand expose a pattern formed on a reticle (or a photomask, etc.) onto awafer (or a glass plate, etc.) coated by photoresist as a substrate.Various types of exposure apparatus, such as, for example, a step andrepeat exposure type (stationary exposure type) projection exposureapparatus such as a stepper, and a step and scan exposure typeprojection exposure apparatus (scanning exposure apparatus) such as ascanning stepper, can be used.

In exposure apparatus, rigidity of: (i) the stages which move andposition a reticle and a wafer, (ii) a support mechanism of the stages,and (iii) a mechanism portion of the support mechanism and the like of aprojection optical system, significantly affects the performancecapability of the apparatus, such as a vibration control performancecapability, an exposure accuracy (overlay accuracy or the like), weightof the mechanism portion, and manufacturing cost of the exposureapparatus. In general, an exposure apparatus having a mechanism portionwith high rigidity, while providing a high apparatus performancecapability, tends to have a heavy mechanism portion, and a highermanufacturing cost. Furthermore, rigidity of the mechanism portion alsois related to the temperature characteristics of the apparatusperformance capability, and the stability of the apparatus performancecapability corresponding to changes of the apparatus performancecapability over time. That is, exposure apparatus having a mechanismportion with high rigidity tend to have good stability with respect tothe apparatus performance capability, and excellent temperaturecharacteristics, but depending on the structure of the mechanismportion, there are cases in which the opposite trend occurs. Forexample, in a mechanism portion, when members with high rigidity arecoupled to each other through members having high rigidity, vibrationcan be easily transmitted, a bi-metal effect is generated at the time oftemperature change (if different materials are used for the members),and the temperature characteristics may be deteriorated.

However, as a result of increasing rigidity of the mechanism portion,when the weight of the mechanism portion increases, there also is apossibility of increased construction cost of the device manufacturingfactory in which exposure apparatus is installed (in order to deal withthe weight of the exposure apparatus). Therefore, conventionally, inorder to maintain high rigidity and perform positioning and scanning ata high speed while reducing the apparatus weight, a lightweight materialwith specific stiffness (value in which rigidity is divided by theweight per unit volume), such as a ceramic, can be used as a material ofa part of the members which constitute a stage.

Furthermore, an exposure apparatus also has been proposed in which thestages and the projection optical system are independently supported byparallel link mechanisms, each having a plurality of rods which canexpand and contract. This system maintains high rigidity in a necessaryportion and lightens the weight of the entire mechanism portion. See,e.g., International Publication No. WO 01/022480.

Thus, in a conventional exposure apparatus, in order to maintain a highdevice capability with respect to vibration control performance or thelike, it is desirable to improve rigidity of a mechanism portion of asupport mechanism or the like, while reducing the weight of themechanism portion. However, among conventional technology, with respectto a method of using a material with specific stiffness and lightweight, the material can be used only for a portion of the mechanismportion due to its high manufacturing cost, the material shape, or thelike, so the lightening of the entire mechanism portion is not yetsignificantly improved. In order to further lighten the entire mechanismportion, it is desirable to change the structure itself of the mechanismportion including the support mechanism of the projection opticalsystem.

Meanwhile, in the method that uses parallel link mechanisms, each havinga plurality of elongatable rods, it is desirable to further improve thelightening of the mechanism portion, and the control accuracy of amovable portion of a stage. However, there is a possibility that controlat the time of scanning and stage positioning also becomes complexbecause the structure of the mechanism portion becomes complex.Additionally, although the projection optical system can be supported byusing the parallel link mechanism, this tends to cause the structure ofthe mechanism portion to become even more complex. In this regard, inrecent exposure apparatus, a thermal distortion amount of the mechanismportion and a fluctuation amount of imaging characteristics of theprojection optical system due to the exposure amount of the exposurebeam and the surrounding temperature are predicted in advance. Accordingto this prediction result, correction of the imaging characteristics,positioning correction of the reticle and the wafer, or the like isperformed during use of the apparatus. However, once the mechanismportion becomes complex, the estimated accuracy of the thermaldistortion amount of the mechanism portion and the fluctuation amount ofthe imaging characteristic deteriorates, and therefore it is possiblethat the exposure accuracy may deteriorate.

Furthermore, conventionally, in order to control the fluctuation amountof the imaging characteristic of the projection optical system due tothe temperature fluctuation, a cooling liquid is supplied to thesurrounding of the projection optical system. In this case, in order toincrease the vibration control performance capability of the exposureapparatus, it is desirable that the vibration of the motive force whichsupplies the cooling liquid should be controlled.

SUMMARY OF THE INVENTION

This invention reflects on the above problems, and has as a firstobject, the provision of a support for a projection optical system usinga relatively simplified, light mechanism in a state in which a highvibration isolation performance capability is obtained.

A second object of this invention is to provide an exposure apparatuswhich can maintain a high device performance capability, such as apositioning performance capability, and obtain high rigidity wherenecessary, and lighten the entire mechanism portion.

A third object of this invention is to reduce vibration when a coolingliquid is supplied to the surrounding of the projection optical system.

In a projection optical device according to a first aspect of thisinvention, a projection optical system that projects an image of apattern is supported by a support device having a flexible structure tosupport the projection optical system, and a positioning device havingan actuator to position the projection optical system.

According to this aspect of the invention, the projection optical systemis supported by a predetermined member (e.g., frame or the like) via theflexible structure. Therefore, in a relatively simplified and lightmechanism, the vibration of the predetermined member is not easilytransmitted to the projection optical system, and the characteristicfrequency of the flexible structure is low. Thus, a high vibrationcontrol performance capability can be obtained.

In this case, the predetermined member and the projection optical systemcan be considered as a rigid structure with high rigidity, whereas theflexible structure has low rigidity. According to this aspect of theinvention, a ratio occupied by members having a rigid structuredecreases within the device, and a flexible structure is used. Ingeneral, a flexible structure has a characteristic opposite to that of arigid structure, is light, has a low cost, and can obtain a preferablecharacteristic of shielding vibration and receiving/transmitting thermaldisplacement depending on the structure of the flexible structure.According to this aspect of the invention, a rigid structure can be usedfor the portion(s) which directly affect(s) device performancecapability, and a flexible structure can be used for the portion(s) thatcouple rigid structures to each other. By this structure, the effects ofthermal displacement and the transmittance of the vibration areminimized or prevented entirely. Therefore, the mechanism portion can belightened while the device performance capability is kept high.

According to this aspect of the invention, in one example, the flexiblestructure includes three coupling members, each of which has a lowercharacteristic frequency in a direction perpendicular to the opticalaxis than in the direction parallel to the optical axis of theprojection optical system. By having three coupling members, theprojection optical system is supported in a stable manner. Furthermore,because the coupling members are comprised of, for example, thin longmembers extending in a direction along the optical axis, thecharacteristic frequency of the coupling members becomes low in adirection perpendicular to the optical axis. Thus, with respect to thevibration having a high frequency component, blurring (deterioration ofthe contrast) of the image position is reduced when the image pattern istransferred via the projection optical system.

In one example, the coupling members include wires or rod membersprovided with flexures on their top end portion and/or their lower endportion. The length of the coupling members preferably is 1 m orgreater. Thus, when the length of the coupling member is 1 m or greater,the characteristic frequency in the direction perpendicular to theoptical axis of the coupling member is substantially 0.5 Hz or less, sothe projection optical system is extremely stably supported with respectto external vibration.

Furthermore, in part of the coupling member, vibration isolationportions can be arranged which reduce the vibration in the optical axisdirection of the projection optical system. By so doing, the vibrationin the direction parallel to the optical axis of the projection opticalsystem can be further reduced.

Furthermore, a frame which supports the coupling members, and thepositioning device which positions the projection optical system withoutcontacting the frame can be provided.

According to this aspect of the invention, the coupling members have aflexible structure, so the frame with a rigid structure and theprojection optical system can be relatively displaced at a lowfrequency. In such a case, by using the positioning device, the relativeposition of the frame and the projection optical system (i.e., thesupport member of the projection optical system) is held at a targetposition, so a preferable characteristic (the lightening of themechanism portion and shielding of vibration and effects of temperaturechanges) due to having a flexible structure can be maintained, and thedevice performance capability, such as stability of the position of theprojection image or the like can be improved. In other words, withrespect to vibration within the frequency range which can be controlledby the positioning device, the projection optical system is supported byan active suspension control method, and with respect to the vibrationat frequencies which exceed this frequency range, the projection opticalsystem is suspended and supported by a passive vibration isolationstructure.

The positioning device also can be provided with displacement sensorswhich measure six degrees-of-freedom of displacement information of theprojection optical system with respect to the frame, and sixdegrees-of-freedom actuators which position the projection opticalsystem in a non-contact manner with respect to the frame. By using themeasurement result of the displacement sensors, the relative position ofthe projection optical system with respect to the frame can becontrolled.

Furthermore, in one example, the support device includes a flangeportion fixed to the side surface of the projection optical system, andthe flange portion kinematically supports a measurement unit having asensor which measures the positional relationship between the projectionoptical system and a predetermined member (e.g., the wafer stage).Therefore, the measurement unit is supported in a state in which thereis a predetermined positional relationship with respect to theprojection optical system, and very little stress is applied, so thepositional relationship between the projection optical system and thepredetermined member can be measured with high accuracy.

In one example, a member (reticle) in which the pattern is formed can beintegrally provided with the projection optical system. This iseffective, for example, when the pattern is transferred by a step andrepeat exposure method. In this case, a micro-moving mechanism can beprovided which micro-moves the reticle with respect to the projectionoptical system. Positioning of the reticle pattern can be performed bythe micro-moving mechanism.

In another example, a frame which supports the flexible structure, abase which is supported to the frame via vibration isolation members,and a stage which drives the member in which the pattern is formed onthe base can be provided. For example, when the pattern is transferredby a scanning exposure method, the member in which the pattern is formedcan be scanned with the stage. Furthermore, the vibration isolationmember is operated as a flexible structure which couples the base andthe frame as a rigid structure, and application of an extra stress tothe base can be suppressed by the vibration isolation member.

In this case, as an example, the vibration isolation member can includepivots or flexures. Pivots or flexures allow a rotational motion, sothey can be vibration isolation members as a simplified mechanism.

Furthermore, in order to cancel a reaction force caused by the movementof the stage, a countermass member which is moved on the base, and aflexure mechanism which supports the countermass member on the base canbe further provided. By so doing, transmission of vibrations between thecountermass member and the base can be even more completely shielded.

According to another aspect of this invention, the projection opticalsystem can be arranged in a downflow environment. The projection opticalsystem is supported, so a gas such as temperature-controlled airsmoothly flows in the vicinity of the projection optical system by adownflow method. Therefore, temperature stability of the projectionoptical system is improved.

Additionally, according to this aspect of the invention, the measurementunit is provided with laser interferometers, and also can be providedwith a local gas flow system which performs a local downflow withrespect to the optical path of the laser beam of the laserinterferometers. By so doing, the measurement accuracy of the laserinterferometers is improved.

In addition, a pipe which is arranged along the side surface of theprojection optical system, from the flexible structure, and a liquidsupply system which supplies a cooling liquid to the pipe, can beprovided. In this structure, the flexible structure also can be used tosupport the pipe, and the temperature stability of the projectionoptical system is improved.

In a projection optical device according to a second aspect of thisinvention, a projection optical system which projects an image of apattern is provided with a liquid supply device which supplies a coolingliquid to the side surface of the projection optical system by a gravitydrive. According to this aspect of the invention, the cooling liquidflows due to gravity, so hardly any vibration is generated.

According to this aspect of the invention, in one example, the liquidsupply device is provided with a pipe which is wrapped around the sidesurface of the projection optical system, and a liquid circulationsystem which circulates the cooling liquid to the pipe according to asiphon principle. With this structure, the cooling liquid can becirculated by a simplified structure.

An exposure apparatus can be provided with a projection optical deviceaccording to various aspects of this invention. Such an exposureapparatus transfers and exposes an image of the pattern onto a substrateby the projection optical system. In this exposure apparatus, when theprojection optical device according to the first aspect of thisinvention is provided, in a portion in which the projection opticalsystem or the like is needed, high rigidity can be obtained, and thedevice performance capability of the vibration isolation performancecapability or the like can be kept high, and the entire mechanismportion can be lightened by suspending and supporting the projectionoptical system.

Furthermore, by supporting the projection optical system as a rigidstructure, via a flexible structure, with respect to a predeterminedmember having a rigid structure, the respective advantages of the rigidand flexible structures can be utilized and combined. Therefore,compared to a conventional example, the ratio occupied by the rigidstructure in the device can be reduced, so without decreasing the deviceperformance capability, such as stability of the position of aprojection image or the like, the mechanism portion can be lightened andmanufactured at a lower cost.

In an exposure apparatus utilizing a projection optical device accordingto the second aspect of this invention, when a cooling liquid issupplied to the surrounding of the projection optical system, thevibration can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings in which like reference numerals designate like elements andwherein:

FIG. 1 is a diagram showing a schematic structure of a projectionexposure apparatus of an embodiment of this invention;

FIG. 2 is a perspective view showing a schematic structure of amechanism portion of a projection exposure device of a first exemplaryembodiment of this invention;

FIG. 3 is a plan view which cuts through a portion showing a flange 18and a projection optical system PL of FIG. 2;

FIG. 4 is a plan view which cuts through a portion showing a modifiedexample of FIG. 3;

FIG. 5A is a perspective view showing a coupling state of the flange 18and a measurement mount 15 of FIG. 2;

FIG. 5B is a perspective view showing a lower end portion of a rod 38Aof FIG. 5A;

FIG. 5C is a perspective view showing a convex portion and a notchportion within the measurement mount 15 of FIG. 5A;

FIG. 6 is a perspective view showing a rod 43 which can be used insteadof rods 38A-38C of FIG. 5A;

FIG. 7 is a perspective view showing a schematic structure of amechanism portion of a projection exposure apparatus of a secondexemplary embodiment of this invention;

FIG. 8 is a diagram showing a liquid supply system of FIG. 7;

FIG. 9 is a schematic structural view showing a mechanism portion of aprojection exposure apparatus of a third exemplary embodiment of thisinvention;

FIG. 10 is a schematic structural view which cuts through a portionshowing a mechanism portion of a projection exposure apparatus of afourth exemplary embodiment of this invention;

FIG. 11 is an enlarged cross-sectional view showing members from acountermass 59 to an intermediate member 55 of FIG. 10;

FIG. 12 is a schematic structural view that cuts through a portion of aprojection exposure apparatus of a fifth embodiment; and

FIG. 13 is a perspective view of the FIG. 12 exposure apparatus.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

The following explains a first exemplary embodiment of this inventionwith reference to FIGS. 1-6. In this embodiment, the invention isapplied to a step and repeat exposure type projection exposure apparatussuch as a stepper or the like, and to a step and scan exposure typeprojection exposure apparatus such as a scanning stepper or the like.

FIG. 1 is a block diagram of different functional units which constitutea projection exposure apparatus of this embodiment. In FIG. 1, a chamberin which the projection exposure apparatus is located, is omitted. InFIG. 1, a laser light source 1 is provided. The laser light source 1 canbe a KrF excimer laser (wavelength 248 μm) or an ArF excimer laser(wavelength 193 μm), for example. The light source also could be adevice which radiates an oscillating laser beam in an ultraviolet rangesuch as an F₂ laser (wavelength 157 nm), a device which radiates aharmonic laser beam in a vacuum ultraviolet range which can be obtainedby wavelength-converting a laser beam in a near infrared range suppliedfrom a solid-state laser light source (YAG or a semiconductor laser, orthe like). A mercury discharge lamp, or the like, which is often used inthis type of exposure apparatus also can be used.

Illumination light for exposure (exposure light) EL as an exposure beamfrom the laser light source 1 irradiates a reticle blind mechanism 7with a uniform irradiation distribution via a homogenizing opticalsystem 2, which is constituted by a lens system and a fly's eye lenssystem, a beam splitter 3, a variable attenuator 4 for adjusting a lightamount, a mirror 5, and a relay lens system 6. The illumination light ELwhich is restricted to a predetermined shape (e.g., a square shape in astep and repeat exposure type, and a slit shape in a step and scanexposure type) by the reticle blind mechanism 7 is irradiated onto areticle R (a mask) via an imaging lens system 8, and an image of anopening of the reticle blind 7 is imaged on the reticle R. Anillumination optical system 9 is constituted by the above-describedhomogenizing optical system 2, the beam splitter 3, the variableattenuator 4, the mirror 5, the relay lens system 6, the reticle blindmechanism 7, and the imaging lens system 8.

In a circuit pattern region formed on the reticle R, the image of theportion irradiated by the illumination light is imaged and projectedonto a wafer W coated by photoresist (a substrate) (a photosensitivesubstrate or a photosensitive body) via a projection optical system PLhaving a reduction projection magnification β and being both-sidetelecentric. For example, the projection magnification β of theprojection optical system PL can be ¼, ⅕, or the like, the imaging sidenumeral aperture NA can be 0.7, and a diameter of a field of view can beapproximately 27-30 mm. The projection optical system PL is a refractivesystem, but a cata-dioptric system or the like also can be used. Thereticle R and the wafer W also can be considered as first and secondobjects, respectively. In the following explanation, a Z axis is definedto be parallel to an optical axis AX of the projection optical systemPL, an X axis extends in a direction parallel to a paper plane of FIG.1, and is perpendicular to the Z axis, and a Y axis extends in adirection perpendicular to a paper plane of FIG. 1. When a projectionexposure apparatus of this example is a step and scan exposure type, adirection (Y direction) along the Y axis is a scanning direction of thereticle R and the wafer W during scanning exposure, and the illuminationregion on the reticle R becomes an elongated shape extending in adirection (X direction) along the X axis, which is a non-scanningdirection.

Furthermore, the reticle R which is arranged on an object surface sideof the projection optical system PL is held by vacuum pressure to areticle stage RST (mask stage). In the case of a step and repeatexposure type, the reticle stage RST (micro-moving mechanism) ismicro-moved on a reticle base (undepicted) in a rotation direction aboutthe X and Y directions and in the Z axis direction, in addition to inthe X and Y directions, so as to position the reticle R. Meanwhile, inthe case of the scanning exposure apparatus, the reticle stage RST(stage) is moved at a constant speed at least in the Y direction(scanning direction) via an air bearing on a reticle base (undepicted).The moving coordinate position (the positions in the X and Y directions,and the rotation angle about the Z axis) of the reticle stage RST issuccessively measured by a moving mirror Mr fixed to the reticle stageRST, a reference mirror Me fixed to the upper portion side surface ofthe projection optical system PL, and a laser interferometer system 10arranged opposite to these mirrors. The laser interferometer system 10includes a laser interferometer main body portion 10 a, a beam splitter10 b which divides the laser beam into a beam for the moving mirror Mrand a beam for the reference mirror Me, and a mirror 10 c which suppliesthe laser beam to the reference mirror Me. Furthermore, the movingmirror Mr, the reference mirror Me, and the laser interferometer system10 actually constitute at least a uniaxial laser interferometer systemin the X direction, and a biaxial or a triaxial laser interferometersystem in the Y direction.

Furthermore, the movement of the reticle stage RST is performed by adriving system 11 comprised of a linear motor, a micro-moving actuator,or the like. The measurement information of the laser interferometersystem 10 is supplied to a stage control unit 14, and the stage controlunit 14 controls the driving system 11 based on the control information(input information) received from a main control system 20 comprised ofa computer which controls the operation of the entire device, and themeasurement information.

Meanwhile, the wafer W arranged on the image plane side of theprojection optical system PL is adsorbed and held on the wafer stage WST(substrate stage) via an undepicted wafer holder. In the case of thestep and repeat exposure type, the wafer stage WST is step-moved in theX and Y directions via an air bearing on a wafer base (undepicted). Inthe case of the scanning exposure type, the wafer stage WST can be movedat a constant speed at least in the Y direction at the time of scanningexposure, and is mounted on a wafer base (undepicted) via an air bearingso as to be step-moved in the X and Y directions. The moving coordinateposition (the positions in the X and Y directions, the rotation angleabout the Z axis) of the wafer stage WST is successively measured by areference mirror Mf fixed to the lower portion of the projection opticalsystem PL, a moving mirror Mw fixed to the wafer stage WST, and a laserinterferometer system 12 arranged opposite to these mirrors. The laserinterferometer system 12 includes a laser interferometer main bodyportion 12 a, a beam splitter 12 b which divides a laser beam into abeam for the moving mirror Mw and a beam for the reference mirror Mf,and a mirror 12 c which supplies a laser beam to the moving mirror Mw.The moving mirror Mw, the reference mirror Mf, and the laserinterferometer system 12 actually constitute at least a uniaxial laserinterferometer system in the X direction, and a biaxial or a triaxiallaser interferometer system in the Y direction. Furthermore, the laserinterferometer system 12 is further provided with a biaxial laserinterferometer for rotation angle measurement about the X and Y axes.

The laser interferometer system 12 (laser interferometer) can beconsidered as one sensor for measuring a positional relationship betweenthe projection optical system PL and the wafer stage WST as apredetermined member. The laser interferometer system 12 is fixed to thebottom surface of a measurement mount 15 (measuring unit) which is anannular flat plate-shaped member arranged on the lower portion sidesurface of the projection optical system PL. Furthermore, in order toreduce fluctuation (fluctuation in an index of refraction) of air on theoptical path of the laser beam to be supplied to the moving mirror Mwand the reference mirror Mf from the laser interferometer system 12, anair duct 16 having flexibility is fixed to the measurement mount 15. Asshown in FIG. 2, the air duct 16 extends substantially parallel to acolumn 33A, one side of an upper portion column 34, and a wire 35B. Gassuch as highly clean air at a controlled temperature and humidity issupplied from a small air conditioning device 17 (see FIG. 2), and thegas is supplied to the optical path of the laser beam of the laserinterferometer system 12 by a local downflow method. Furthermore, inorder to couple a portion of the air duct 16 with the wire 35B, a fixedmount 16M (support member) is arranged in the vicinity of a movableportion of the wire 35B. A local gas flow system is constituted of thesmall air conditioning device 17 and the air duct 16. By so doing, themeasurement accuracy of the laser interferometer system 12 is improved.Additionally, a plurality of air ducts 16 also can be provided.

In FIG. 1, the movement of the wafer stage WST is performed by a drivingsystem 13 comprising an actuator such as a linear motor, a voice coilmotor (VCM), or the like. The measurement information of the laserinterferometer system 12 is supplied to the stage control unit 14, andthe stage control unit 14 controls the operation of the driving system13 based on the measurement information and the control information(input information) received from the main control system 20.

Additionally, the wafer stage WST is moved to control its position(focus position) in the Z direction of the wafer W, by a Z-levelingmechanism which also controls an inclination angle about the X and Yaxes. Furthermore, an oblique incident type multi-point autofocus sensor(23A, 23B) is fixed to the measurement mount 15 of the lower sidesurface of the projection optical system PL. The oblique incident typemulti-point autofocus sensor (23A, 23B) is composed of a projectionoptical system 23A which projects a slit image onto a plurality ofmeasurement points on the surface of the wafer W, and a light receivingoptical system 23B which detects the information relating to thehorizontal shift amount of the image in which these slit images werere-imaged by receiving the reflected light from the surface, andsupplies this information to the stage control unit 14. The stagecontrol unit 14 calculates a defocus amount from the image plane of theprojection optical system PL in the plurality of measurement points byusing the information of the horizontal shift amount of the slit image,and drives the Z leveling mechanism within the wafer stage WST by theautofocus method so that the focus amount is maintained withinpredetermined control accuracy at the time of exposure. A detailedstructure of one type of an oblique incident type multi-point autofocussensor is disclosed in, e.g., Japanese Laid-Open Patent Application1-253603.

Furthermore, the stage control unit 14 includes a control system on thereticle side which optimally controls the driving system 11 based on themeasurement information received from the laser interferometer system10, and a control system on the wafer side which optimally controls thedriving system 13 based on the measurement information received from thelaser interferometer system 12. If the projection exposure apparatus ofthis example is a scanning exposure type, when the reticle R and thewafer W are synchronously scanned at the time of scanning exposure, bothcontrol systems coordinate and control the respective driving systems 11and 13. Furthermore, the main control system 20 mutually communicateswith the respective control systems in the stage control unit 14 withrespect to parameters and commands, and the respective control systemsin the stage control unit 14, and optimally performs exposure processingin accordance with a program designated by an operator. Because of this,an undepicted operation panel unit (including an input device and adisplay device) is provided, and forms an interface between the operatorand the main control system 20.

Furthermore, at the time of exposure, it is desirable to align thereticle R and the wafer W in advance. Therefore, in the projectionexposure apparatus of FIG. 1, a reticle alignment system (RA system) 21which sets the reticle R at a predetermined position, and an off-axistype alignment system 22 which detects a mark on the wafer W areprovided. The alignment system 22 (mark detection system) is fixed tothe measurement mount 15. The multi-point autofocus sensors (23A, 23B)and the alignment system 22 can be considered as one sensor whichmeasures the positional relationship between the projection opticalsystem PL and the wafer stage WST or the wafer W (predetermined member).

Furthermore, when the laser light source 1 is an excimer laser lightsource, a laser control unit 25 which is controlled by the main controlsystem 20 is provided. Laser control unit 25 controls modes (one pulsemode, burst mode, waiting mode, or the like) of pulse oscillation of thelaser light source 1, and controls a discharging high voltage of thelaser light source 1 in order to adjust an average light amount of thepulse laser light to be radiated. Furthermore, a light amount controlunit 27 controls a variable attenuator 4 in order to obtain anappropriate exposure dose based on the signal received from aphotoelectric detector 26 (integrator sensor) which receives part of theillumination light divided by the beam splitter 3, and sends intensity(light amount) information of the pulse illumination light to the lasercontrol unit 25 and the main control system 20.

Additionally, in FIG. 1, in the case of a step and repeat exposure typeapparatus, an operation which, in the presence of the illumination lightIL, projects a pattern of the reticle R onto one shot area on the waferW via the projection optical system PL, and an operation whichstep-moves the wafer W via the wafer stage WST in the X and Y directionsare repeated by a step-and-repeat method. Meanwhile, in the case of ascanning exposure type apparatus, according to the scanning exposureoperation, a pattern image of the reticle R is transferred to the shotarea, in a state in which irradiation of the illumination light IL tothe reticle R is provided, the image which passed through part of thepattern of the reticle R of the projection optical system PL isprojected onto one shot area on the wafer W, and, using projectionmagnification β of the projection optical system PL as a speed ratio,the reticle stage RST and the wafer stage WST are synchronously moved(synchronized scanning) in the Y direction. Then, by repeating theoperation in which irradiation of the illumination light IL is stoppedand the wafer W is step-moved in the X and Y directions via the waferstage WST and the above-mentioned scanning exposure operation, thepattern image of the reticle R is transferred onto all of the shot areason the wafer W by a step-and-scan method.

The following explains the details of a structure of the mechanismportion of the projection exposure apparatus of this example of theinvention. This mechanism portion also can be considered as a projectionoptical device provided with a projection optical system PL. Thefollowing explains when the projection exposure apparatus of thisexample is a step and repeat exposure type.

FIG. 2 shows a schematic structure of the mechanism portion of theprojection exposure apparatus of this example. In FIG. 2, shortcylindrical seats 32A, 32B (the third seat, 32C, is undepicted) arearranged at three locations located at the vertices of a triangle on thefloor surface. Long columns 33A, 33B, 33C are located on the respectivethree seats 32A, 32B, 32C. The columns are arranged in a state so thatposition shifting is not generated, thus the thin, long cylindricalcolumns 33A, 33B, 33C slant inwardly to some degree as shown in FIG. 2(rather than being perfectly vertical). The three columns 33A-33C arearranged so that the spacing between their upper portions is more narrowthan the spacing between their lower ends, and a substantially triangleframe-shaped upper column 34 is fixed on the top surfaces of the columns33A-33C. A column structural body comprised of the columns 33A-33C andthe upper column 34 corresponds to a frame which suspends the projectionoptical system PL.

That is, the projection optical system PL is arranged within a spacesurrounded by the columns 33A-33C, and the flange 18 (support member) isintegrally fixed to the projection optical system PL so as tosubstantially surround the side surface of the center in the Z directionof the projection optical system PL. The flange 18 can be integratedwith a lens barrel of the projection optical system PL. Additionally,one end of coil springs 36A, 36B, 36C (vibration isolation portions),which are identical to each other, is fixed to the respective centerportion of each of the three pieces of the upper column 34. The flange18 is coupled to the other end of the coil springs 36A, 366B, 36C viawires 35A, 35B, 35C, which are identical to each other and made ofmetal. The wire 35A and the coil spring 36A correspond to one couplingmember. In the same manner, other wires 35B, 35C and coil springs 36Band 36C correspond to two other coupling members. These coupling membersare substantially parallel to each other and parallel to the Z axis. Inthis example, the direction (−Z direction) toward the floor surface is avertical direction, and a plane (XY plane) perpendicular to the Z axisis a substantially horizontal plane. Therefore, from the upper column34, the projection optical system PL and the flange 18 are suspended andsupported via the three coupling members.

In this case, the optical axis of the projection optical system PL isparallel to the Z axis, and the characteristic frequency of the couplingmembers of this example is lower in the direction perpendicular to theoptical axis than in the direction parallel to the optical axis of theprojection optical system PL. The coupling members vibrate like apendulum in a direction perpendicular to the optical axis, so if thelength in the Z direction of the coupling members is L, and theacceleration constant is G (=9.8 m/s²), as shown below, the longer thelength L becomes, the lower the characteristic frequency fg in thedirection perpendicular to the optical axis becomes. $\begin{matrix}{{fg} = {\frac{1}{2\pi}\sqrt{G/L}}} & (1)\end{matrix}$

The lower the characteristic frequency fg becomes, the better thevibration isolation performance capability (capability which preventsvibration of the floor from being transmitted to the projection opticalsystem PL) in the direction perpendicular to the optical axis of theprojection optical system PL becomes. Thus, in order to improve thevibration isolation performance capability, the longer the length L ofthe coupling members becomes, the better. However, on the other hand, inorder to stably support the projection optical system PL, it ispreferable that the flange 18 which is suspended by coupling membersshould be fixed in the vicinity of a center of gravity in the Zdirection of the projection optical system PL. Furthermore, in order tooptimally reduce the size of the projection exposure apparatus, it ispreferable that the height of the upper column 34 should not be higherthan the upper end portion of the projection optical system PL. Fromthis perspective, the length L of the coupling members becomesapproximately ½ or less of the Z direction length of the projectionoptical system PL.

As an example, the length L of the coupling members is set to besubstantially 0.5 m. If this value is applied to equation (1), thecharacteristic frequency fg becomes a small value, i.e., 0.7 Hz.Furthermore, if the length L of the coupling members is set to be lm orgreater, according to equation (1), the characteristic frequency fgbecomes approximately 0.5 Hz which is sufficiently low for the vibrationisolation performance in the projection exposure apparatus.fg<0.5 (Hz)  (2)

Therefore, for example, if it is possible in view of the length of theprojection optical system PL, it is preferable that the length of thecoupling members be set approximately between lm and several m.

Furthermore, the characteristic frequency in the optical axis directionof the projection optical system PL of the wires 35A-35C in the couplingmembers becomes much higher than the characteristic frequency fg.However, for example, among the vibrations transmitted to the uppercolumn 34 via the columns 33A-33C from the floor, most of the vibrationcomponents in the optical axis direction are absorbed by the coilsprings 36A-36C (vibration isolation portions), so a high vibrationisolation performance capability can be obtained in a direction parallelto the optical axis.

Furthermore, for example, between the columns 33A-33C and the uppercolumn 34, it is possible to arrange a vibration isolation member suchas a coil spring or an air damper. In such a case, the coil springs36A-36C in the coupling members can be omitted.

In addition, in this example, the reticle stage RST (here, micro-movingmechanism) is integrally fixed to the upper portion of the projectionoptical system PL. The reticle R (member in which a pattern is formed)is held by the reticle stage RST. The reticle stage RST is provided witha base portion 311B fixed to the projection optical system PL, an Xstage 31X which can be micro-moved in the X direction with respect tothe base portion 31, and a Y stage 31Y which can be micro-moved in the Ydirection with respect to the X stage 31X and that holds the reticle R.On the pattern formation surface of the reticle R of this example, apair of alignment marks RMA and RMB are formed at a predeterminedinterval in the X direction. Reticle alignment systems (RA system) 21A,21B are arranged above the alignment marks RMA, RMB via the respectivemirrors 28A, 28B. The pair of RA systems 21A, 21B corresponds to the RAsystem 21 of FIG. 1.

The projection exposure apparatus of this example is a step and repeatexposure type, and before exposure, after positioning of the alignmentmarks RMA and RMB of the reticle R by using the RA systems 21A, 21B, itis not necessary to move the reticle R. Because of this, the laserinterferometer system 10 on the reticle side of FIG. 1 is not providedin the projection exposure apparatus of FIG. 2.

Furthermore, the mirrors 28A, 28B, and the RA systems 21A, 21B are fixedto an undepicted column coupled with the upper column 34, and anillumination system sub-chamber 19 which stores the illumination opticalsystem 9 of FIG. 1 is fixed with respect to the column. In this case,the laser light source 1 of FIG. 1 is arranged on the floor outside thecolumns 33A-33C of FIG. 2 as an example, and the illumination light ILto be emitted from the laser light source 1 is guided to theillumination optical system 9 via an undepicted beam transmittingsystem.

In addition, a wafer base WB is arranged via a vibration isolation pad(undepicted) on the floor surface below the projection optical systemPL, and the wafer stage WST which holds the wafer W on the wafer base WBis movably arranged thereon via an air bearing. On top of the waferstage WST, a reference mark member 29 is fixed in which a reference markis formed to perform alignment of the reticle R and the wafer W.

Thus, the projection optical system PL having a rigid structure of thisexample is suspended and supported via the coil springs 36A-36C and thewires 35A-35C, which function as coupling members having a flexiblestructure, with respect to the upper column 34, which has a rigidstructure. In this structure, a high vibration isolation performancecapability can be obtained, and the mechanism portion can besignificantly lightened. However, there is a possibility that therelative position of the projection optical system PL and the uppercolumn 34 can change at a relatively low frequency of vibration.Therefore, in order to maintain the relative position of the projectionoptical system PL and the upper column 34 (and the columns 33A-33C) in apredetermined state, as shown in FIG. 3, a positioning device of anon-contact type is provided.

FIG. 3 is a plan view of the projection optical system PL and the flange18 of FIG. 2. In FIG. 3, arm portions 37A, 37B, 37C, which extend towardthe flange 18 are fixed to the columns 33A, 33B, 33C. The arm portions37A-37C are arranged at a substantially 120° interval about the opticalaxis AX of the projection optical system PL. Furthermore, between thefirst arm portion 37A and the flange 18, a first actuator 40A whichdisplaces the flange 18 in the Z direction and a second actuator 41Awhich displaces the flange 18 in a circumferential direction areprovided. Voice coil motors can be used for the actuators 40A, 41A. Inaddition, a non-contact electromagnetic actuator, e.g., an EI core typeor the like, also can be used as actuators 40A and 41A.

Additionally, on the flange 18 in the vicinity of the arm portion 37A, afirst biaxial acceleration sensor 39A is provided, which detectsacceleration in the Z direction and in the circumferential direction ofthe flange 18. The biaxial acceleration information detected by theacceleration sensor 39A is supplied to a controller 42, and thecontroller 42 drives the actuators 40A, 41A so that the flange 18 can bemaintained stationary with respect to the arm portion 37A (and thus theupper column 34 of FIG. 2) or with respect to the earth based on theacceleration information. In this embodiment, the accelerationinformation is used to servo-control the actuators 40A, 41A to maintainthe flange 18 (and thus the projection optical system PL) stationary.Prior to performing the servo-control, the flange 18 (and thus theprojection optical system PL) is located at a reference position atwhich the flange 18 and the arm portions 37A-37C have a predeterminedrelationship to each other (e.g., such that the actuators will beeffective at driving the flange). The flange 18 can be moved to thereference position based on the output of one or more (e.g., three)displacement sensors (not shown), which can be, e.g., an interferometer,a capacitance type displacement sensor, an eddy current displacementsensor, etc.

In FIG. 3, between the second arm portion 37B and the flange 18, andbetween the third arm portion 37C and the flange 18 as well, third andfifth actuators 40B and 40C are provided which displace the flange 18 inthe Z direction, and fourth and sixth actuators 41B and 41C are providedwhich displace the flange 18 in the circumferential direction. Thestructures of the actuators 40B, 41B and 40C, 41C are the same as theactuators 40A, 41A. Furthermore, on the flange 18 in the vicinity of thearm portions 37B and 37C, the second and third biaxial accelerationsensors 39B and 39C are provided, which detect the acceleration in the Zdirection and in the circumferential direction of the flange 18. Theacceleration information of the acceleration sensors 39B and 39C also issupplied to the controller 42, and the controller 42 drives theactuators 40B, 41B and 40C, 41C so that the flange 18 can be maintainedrelatively stationary with respect to the respective arm portions 37Band 37C (and thus the upper column 34 of FIG. 2) or with respect to theearth based on the acceleration information.

As acceleration sensors 39A-39C, displacement sensors, a piezoelectrictype acceleration sensor which detects a voltage generated by apiezoelectric element or the like, a semiconductor type accelerationsensor which monitors changes of a logical threshold value voltage of aCMOS converter, e.g., according to the displacement and distortion ofthe mass, or the like can be used. An advantage of using accelerometersis that once the servo-control is started, the flange 18 (and thus theprojection optical system PL) can be maintained stationary in space, asopposed to being maintained stationary only relative to the arm portions37A-37C, which can move slightly due to, e.g., vibrations that might betransmitted from the ground through the seats 32A-32C. It also ispossible to forego using the acceleration sensors 39A-39C, and toinstead use one or more position sensors which directly measure therelative position between the flange 18 and the arm portions 37A-37C(and thus the upper column 34). A position sensor, for example, an eddycurrent displacement sensor, a capacitance type displacement sensor, anoptical type sensor, or the like can be used.

Thus, the positioning device of the projection optical system PL and theflange 18 is constituted by the six-axis acceleration sensors 39A-39C(displacement sensors), the six-axis actuators 40A-40C, 41A-41C, the sixposition sensors and the controller 42. By this positioning device, therelative position, in the X, Y and Z directions, of the projectionoptical system PL with respect to the upper column 34 (assuming that theupper column 34 does not vibrate or otherwise move), and the relativerotation angles about the X, Y, and Z axes are maintained in a constantstate (predetermined state). The response frequency of the actuators40A-40C, 41A-41C is approximately 10 Hz, and thus with respect tovibrations up to the response frequency, the projection optical systemPL of this example is supported by an active suspension method.Furthermore, with respect to vibrations of a frequency which exceedsthis, the projection optical system PL is suspended and supported by apassive vibration isolation structure.

In FIG. 3, the three columns 33A-33C are used. However, as shown in FIG.4, four columns 33A-33D also can be used.

FIG. 4 is a plan view showing the projection optical system PL and theflange 18 when the four columns 33A-33D are used. In this figure, thecolumns 33A-33D are stably arranged so that their spacing at their upperportion is narrower at a position of vertices of a substantially squareshape, compared to at the lower ends of the columns 33A-33D.Furthermore, a square frame-shaped upper column 34A is fixed to theupper portion of the columns 33A-33D, and the wires 35A-35C whichsuspend the flange 18 are coupled to three locations of the upper column34A via the coil springs 36A-36C of FIG. 2.

In this case, the two columns 33A and 33B are arranged so as to sandwichthe projection optical system PL in the X direction, and the column 33Cis arranged in the +Y direction of the projection optical system PL. Inaddition, between the flange 18 and the arm portion 37A fixed to thecolumn 33A, the first and second actuators 40A, 41A are provided whichdrive the flange 18 in the Z and Y directions, respectively, and thethird and fourth actuators 40B, 41B which drive the flange 18 in the Zand Y directions, respectively are provided on arm portion 37B.Furthermore, between the flange 18 and the arm portion 37C fixed to thecolumn 33C, the fifth and sixth actuators 40C and 41C are provided whichdrive the flange 18 in the Z and X directions, respectively.Furthermore, the biaxial acceleration sensors 39A-39C are arranged onthe upper portion of the flange 18 in the vicinity of the arm portions37A-37C.

In the structure of FIG. 4, the projection optical system PL (and theflange 18) can be driven in the X direction by the actuator 41C, and theprojection optical system PL (and the flange 18) can be driven by theactuators 41A, 41B in the Y direction and in the rotation directionabout the Z axis, so the actuators 41A-41C can be easily controlled.

In FIG. 2, on the bottom surface of the flange 18 (support member) ofthe projection optical system PL, an annular flat-shaped measurementmount 15 (measurement unit) is coupled via the three cylindrical rods38A, 38B, 38C (link members), which extend substantially parallel to theZ axis. That is, the measurement mount 15 is stably coupled to theflange 18 by a kinematic support method comprised of a semi-three-pointsupport. The alignment system 22, the air duct 16, and the laserinterferometer system 12 are fixed to the measurement mount 15.

FIG. 5A shows a state in which the flange 18 and the measurement mount15 of FIG. 2 are coupled via the rods 38A-38C. In FIG. 5A, flexures 38Aband 38Aa whose diameters are made small are formed in both end portionsof the rod 38A. Flexures also are formed on both end portions of the twoother rods 38B, 38C.

As shown in FIG. 5B, in one flexure 38Aa of the rod 38A, displacement inthe five degrees-of-freedom other than expansion in the Z direction ispossible. In the same manner, displacement in five degrees-of-freedomalso is possible in the other flexure 38Ab of the rod 38A of FIG. 5A,and in the flexures of both end portions of the other two rods 38B, 38C.Thus, virtually no stress is applied between the flange 18 and themeasurement mount 15. Therefore, high measuring accuracy can be obtainedin the laser interferometer system 12 or the like fixed to themeasurement mount 15.

Furthermore, a slot and a pad are formed at three locations in thevicinity of the aperture at the center of the measurement mount 15 (theaperture into which the projection optical system PL is inserted), andthe three pads contact the side surface of the projection optical systemPL.

FIG. 5C shows a slot 15 a 2 and a pad 15 a 1 of the measurement mount 15as a flexure. Because of this structure, the pad 15 a 1 allowsdisplacement in five degrees-of-freedom including the displacement inthe Z direction and in the radius direction about the optical axis withrespect to the side surface of the projection optical system PL, anddisplacement in the rotation direction about the Z, X and Y axes.Therefore, virtually no stress is applied between the measurement mount15 and the projection optical system PL, so the imaging characteristicof the projection optical system PL can be stably maintained.

Furthermore, instead of the rods 38A-38C in which the flexures areformed on both end portions as shown in FIG. 5A, a rod 43 (link member)shown in FIG. 6 can be used. In FIG. 6, in the upper end portion of therod 43, slots 43 a, 43 b are formed in two perpendicular directions, andthe lower end portion of the rod 43 is fixed to a member (in the exampleof FIG. 5A, the measurement mount 15), and includes slots 43 b, 43 a,which are symmetrical to the upper end portion. Even if the rods 38A-38Cof FIG. 5A are replaced with three rods that are the same as the rod 43of FIG. 6, at least displacement in five degrees-of-freedoms is possiblein both end portions of the rod 43, so the flange 18 and the measurementmount 15 are coupled in a state in which virtually no stress is applied(i.e., they are attached using a kinematic support method).

In FIG. 2, the projection exposure apparatus of this example is arrangedin a downflow environment, and a predetermined gas (e.g., air) having acontrolled temperature and humidity, and being subjected to particleprevention processing, is supplied to the wafer base WB via the sidesurface of the projection optical system PL, from the illuminationsystem sub-chamber 19 side. The projection optical system PL of thisexample is suspended and supported by the upper column 34, and there areno members in the way that would prevent predetermined gas flow.Therefore, the predetermined gas can be supplied smoothly in thedownward direction, the temperature stability of the projection opticalsystem PL is improved, and the stability of the imaging characteristicsis improved.

Thus, in the projection exposure apparatus of FIG. 2 of this example,the projection optical system PL and the flange 18 of a rigid structureare suspended and supported by an active suspension method via the coilsprings 36A-36C and the wires 35A-35C, as coupling members having aflexible structure, with respect to the upper column 34, which has arigid structure. Because of this, the following advantages are possible.

(1) The projection exposure apparatus of this example is constituted byan extremely simplified structural body, the mechanism portion can belightened, and the manufacturing cost can be reduced.

(2) The projection optical system PL is suspended and supported, andparticularly the characteristic frequency of vibration in the directionperpendicular to the optical axis of the coupling member (projectionoptical system PL) is extremely low, so the effects of vibrations fromthe floor surface are significantly reduced. Therefore, an apparatusperformance capability, such as a vibration isolation performancecapability, exposure accuracy (overlay accuracy), or the like can beimproved. Furthermore, even if vibration becomes an issue, the vibrationtransmission path can be easily identified, and for example, acountermeasure can be easily performed, e.g., in which a vibrationisolation member is added to the portion in which vibration istransmitted, or the like.

(3) When the environment temperature of the projection exposureapparatus changes, thermal deformation of the structural body also canbe easily predicted, so by using a temperature sensor, and measuring thetemperature of each part of the structural body, based on themeasurement result, a positioning error or the like can be corrected.

(4) There is a large space in the vicinity of the projection exposureapparatus. Thus, when the next generation exposure apparatus is designedand customized, there is no need to change a platform (a supportmechanism or the like of a base, a column, and a projection opticalsystem). Therefore, the degree of freedom for design becomes large, anda preferable structure is possible for a so-called modular design.

Second Embodiment

The following explains a second exemplary embodiment of this inventionwith reference to FIGS. 7 and 8. With respect to the projection exposureapparatus of this example, a mechanism which stabilizes the temperatureof the projection optical system PL is added to the projection exposureapparatus of FIG. 2. In FIGS. 7 and 8, the same symbols are used for theportions corresponding to the portions of FIG. 2, and their detaileddescription is omitted. Furthermore, in FIG. 7, in order to clarifyunderstanding of the additional structure, the air duct 16 and the smallair conditioning device 17 of FIG. 2 are omitted.

FIG. 7 shows a schematic structure of a mechanism portion of theprojection exposure apparatus of this example. In FIG. 7, a recoverytank 45 which collects a cooling liquid is provided on the floor, asupply tank 48 which stores the liquid is provided in the vicinity ofone vertex of the triangle frame-shaped upper column 34, and a supportmember 49B which connects later-mentioned tubes, is provided in thevicinity of another vertex of the upper column 34. As a cooling liquid,water or a fluorine group inert liquid (e.g., FLUORNERT (manufactured byU.S. 3M Corporation)) can be used. A so-called coolant also can be usedas the liquid. In terms of environment, water is preferable as theliquid.

The recovery tank 45 is coupled to a pipe 46A (see FIG. 8), which iscoupled to a temperature control device which adjusts the temperature ofthe liquid passing through its inside to a target temperature and whichhouses a pump 47, which in turn is coupled to the upper portion of thesupply tank 48 via the pipe 46B. The bottom portion of the supply tank48 is coupled to the pipe 46D via the pipe 46C which is downwardlyextended along the wire 35B. The pipe 46D includes a pipe which coolsthe projection optical system PL from a downward direction to an upwarddirection of the projection optical system PL, and is coupled to thepipe 46E via a pipe which extends along the flange portion 18 toward theupper portion of the projection optical system PL. The pipe 46E includesa pipe which is upwardly extended along the wire 35A and is coupled tothe recovery tank 45. Part of the pipe 46C is held by the fixed mount49A (support member) which is fixed to the movable portion of the wire35B, and the pipe 46E is fixed by a fixed mount (undepicted) attached tothe movable portion of the coil spring 36A. After the pipe 46E is fixedby the support member 49B, it extends along the column 33A.

The pipes 46A-46E are formed of composite resin or the like havingflexibility, and the height of the supply tank 48 is greater than thatof the recovery tank 45, so even if the pipe moves up and down, asdescribed later, the cooling liquid can be circulated by a siphonprincipal (an operation which pushes the liquid out by using heightdifference) between the supply tank 48 and the recovery tank 45. Thus,the liquid supply device includes the recovery tank 45, the pipes46A-46E, the temperature control device housing a pump 47, and thesupply tank 48.

FIG. 8 shows the liquid flow provided by the liquid supply device ofFIG. 7. In FIG. 8, the liquid within the recovery tank 45 is suctionedby the pipe 46A as shown by an arrow A1 due to the pump 47 housed in thetemperature control device. After being cooled in the temperaturecontrol device, the liquid is supplied to the supply tank 48 via thepipe 46B as shown by an arrow A2. Then, the liquid within the supplytank 48 flows into the pipes 46C-46E as shown by arrows A3-A4 and iscollected by the recovery tank 45. At this time, depending on the case,there is a possibility that the pipe 46E goes through a position higherthan the tank 48, but once the liquid begins circulating, thecirculation is maintained by the siphon principle. Therefore, when thecooling liquid is supplied to the side surface of the projection opticalsystem PL, a vibration source does not exist because the liquid ispushed out by using the gravitational force caused by the heightdifference only, so a vibration control performance capability does notdeteriorate.

Third Embodiment

The following explains a third embodiment of this invention withreference to FIG. 9. In this example, in the same manner as in theembodiment of FIG. 2, this invention is applied to a step and repeatexposure type projection exposure apparatus. In FIG. 9, the same symbolsare used for the portions corresponding to the portions of FIG. 2, andtheir detailed description is omitted.

FIG. 9 shows a schematic structure of a mechanism portion of theprojection exposure apparatus of this example. In FIG. 9, three columns33A, 33B (the third column, 33C, is undepicted) are fixed to the floor F(which also could be a supporting frame located on a floor), and extendparallel to the Z axis. The upper column 34B is supported on the columns33A, 33B, 33C via passive-type vibration isolation members 51A, 511B(and undepicted 51C), which include, for example, an air damper and/or acoil spring. Furthermore, the flange 18 (support member) is integralwith the projection optical system PL, and is fixed thereto so as tosurround the side surface at substantially the center of the projectionoptical system PL in the Z direction. Vibration isolation members 53A,53B, 53C, e.g., a leaf spring, are fixed to three locations of the uppercolumn 34B. Furthermore, from the vibration isolation members 53A, 53B,53C, the flange 18 (and thus the projection optical system PL) issuspended via rods 52A, 52B, 52C, which are substantially parallel tothe Z axis, and in which flexures which are identical to each other areformed on both ends.

In this case, the vibration isolation member 53A and the rod 52Acorrespond to one coupling member. In the same manner, the othervibration isolation members 53B, 53C and rods 52B, 52C correspond to twoother coupling members. These coupling members are substantiallyparallel to each other and parallel to the Z axis. In this example, therods 52A-52C can be easily displaced in a direction perpendicular to theoptical axis AX of the projection optical system PL, so thecharacteristic frequency of the coupling members is lower in thedirection perpendicular to the optical axis than in the directionparallel to the optical axis AX of the projection optical system PL, inthe same manner as in the first embodiment. The length L of the couplingmembers is set at substantially 0.5 m for example. If this value isapplied to equation (1), the characteristic frequency of the couplingmembers in the direction perpendicular to the optical axis AX becomes asmall value, e.g., approximately 0.7 Hz. Furthermore, if the length L ofthe coupling members is set at lm or greater, according to equation (1),the value becomes approximately 0.5 Hz or less, which is suitable forthe characteristic frequency of the projection exposure apparatus.

Furthermore, the characteristic frequency in the optical axis AXdirection of the rods 52A-52C within the coupling members isconsiderably greater than the characteristic frequency in the directionperpendicular to the optical axis AX. However, for example, most of thevibration transmitted to the columns 33A, 33B, 33C from the floor isattenuated by the vibration isolation members 51A, 51B, 51C, and thusthe vibration in the optical axis AX direction is hardly transmitted tothe upper column 34B. Thus, the projection optical system PL is stablysupported.

Furthermore, in order to control the relative position of the flange 18and the projection optical system PL with respect to the columns 33A,33B, 33C, between the columns 33A, 33B, and 33C and the flange 18, thebiaxial actuators 54A and 54B (and undepicted 54C) are arranged whichcontrol the relative position in the Z direction and in thecircumferential direction. Furthermore, position sensors (undepicted)for measuring the position in six degrees-of-freedom are arranged on theflange 18. Based on the measurement information of the position sensor,by driving the six-axes actuators, the relative position of the flange18 and the projection optical system PL is controlled.

Other parts of the structure are the same as in the first embodiment ofFIG. 2. In this example as well, the reticle stage RST which micro-movesthe reticle R is integrally fixed to the projection optical system PL,and the measurement mount 15 is supported by a kinematic support methodvia the three rods 38A-38C from the bottom surface of the flange 18. Thelaser interferometer system 12, or the like, is fixed to the measurementmount 15. Furthermore, the image of the whole reticle R pattern istransferred to the respective shot areas on the wafer W via theprojection optical system PL.

According to this example, the projection optical system PL is suspendedand supported by the upper column 34B. Therefore, in the same manner asin the first embodiment, a vibration isolation performance capabilitycan be improved, and the mechanism portion can be lightened.Furthermore, the rods 52A-52C are used as coupling members, so even whenthe projection optical system PL is heavy, the projection optical systemPL can be stably supported.

Fourth Embodiment

The following explains a fourth exemplary embodiment of this inventionwith reference to FIGS. 10 and 11. In this example, this invention isapplied to a scanning exposure type projection exposure apparatus. InFIGS. 10 and 11, the same symbols are used for the portionscorresponding to the portions of FIGS. 2 and 9, and their detaileddescription is omitted.

FIG. 10 shows a schematic structure of a mechanism portion of aprojection exposure apparatus of this example. In this figure, the threecolumns 33A, 33B (the third column, 33C, is undepicted) are fixed to thefloor F (or a frame located on the floor), and extend parallel to the Zaxis. An intermediate member 55, which has a flat shape and can beelastically deformed to some degree, and in which an aperture into whichan end portion of the projection optical system PL is inserted, issupported on the columns 33A-33C via the passive type vibrationisolation members 51A, 51B (and undepicted 51C). Furthermore, the flange18 (support member) is integrally provided with the projection opticalsystem PLA, and is fixed thereto so as to surround the side surface atsubstantially the center, in the Z direction, of the projection opticalsystem PLA of this example. The flange 18 and the projection opticalsystem PLA are suspended via the three rods 52A, 52B, 52C (the rod 52Bis positioned in front of the projection optical system PLA in the samemanner as in the example of FIG. 9, and is not depicted in FIG. 10),which are identical to each other and extend substantially parallel tothe Z axis, at three locations from the intermediate member 55. Flexuresare formed on both end portions of the rods 52A-52C. In this case, therods 52A-52C correspond to three coupling members, and a columnmechanism body including the columns 33A, 33B, 33C the vibrationisolation members 51A, 51B, 51C and the intermediate member 55corresponds to a frame which suspends these coupling members.

Furthermore, for example, via rotatable pivots 58A, 58B (a third pivot(58C) is undepicted) (vibration isolation members) at three locations ofthe upper surface of the intermediate member 55, a reticle base 57 isprovided which is a thick, flat plate, and in which an aperture isformed for passing illumination light beam EL. On the reticle base 57,via an air bearing, a reticle stage 60 is provided which adsorbs andholds the reticle R so as to be movable within the XY plane. Thescanning direction of the reticle R during scanning exposure of thisexample is the Y direction (direction perpendicular to the paper planeof FIG. 10), and in order to cancel a reaction force generated when thereticle stage 60 is driven in the Y direction, a rectangularframe-shaped countermass 59 is provided on the reticle base 57, so as tosurround the reticle stage 60. Furthermore, a first Y-axis linear motor61 is constituted by a movable part 61 a located at the end portion inthe +X direction of the reticle stage 60, and a stator 61 b located on(or in) the countermass 59. In symmetry to this linear motor 61, asecond Y-axis linear motor 62 is constituted by a movable part 62 alocated at the end portion in the −X direction of the reticle stage 60,and a stator 62 b located on (or in) the countermass 59. The first andsecond Y-axis linear motors 61 and 62 each drive the reticle stage 60 inthe Y direction with respect to countermass 59. At this time, thecountermass 59 moves in the opposite direction, so the driving reactionforce is canceled, and the generation of vibration is controlled. Thisis not depicted, but the reticle stage 60 also can be provided with amicro-moving mechanism for the rotation directions about the X, Y, and Zaxes.

Furthermore, a measurement mount 56 is fixed to the intermediate member55, and in this measurement mount 56, based on a reference mirror Me(see FIG. 11) on the side surface of the projection optical system PLA,a laser interferometer system 10 (similar to FIG. 1) is incorporatedwhich measures the position in the rotation direction about the X, Y,and Z axes of the reticle stage 60. Additionally, a reticle stage systemRSTA which drives the reticle R includes the intermediate member 55, thereticle base 57, the reticle stage 60, the countermass 59, and themeasurement mount 56.

FIG. 11 shows an enlarged cross-sectional view of the members from thecountermass 59 to the intermediate member 55 of FIG. 10. In FIG. 11, thecountermass 59 is arranged on the reticle base 57 via a plurality of airpads 62A, 62B (others are omitted). In this structure, the air pads 62A,62B are smoothly moved on the reticle base 57 by an air bearing method.Furthermore, the bottom surface of the countermass 59 and the air pads62A, 62B are each coupled via a flexure 63 (flexure mechanism), which isa member having a cross-sectional area that is small, in a state inwhich relative rotation is possible to a degree.

In FIG. 10, in this example as well, in order to control the relativeposition in the six degrees-of-freedom of the flange 18 and theprojection optical system PLA with respect to the columns 33A, 33B, 33C,six-axis non-contact actuators 54A, 54B (the remaining biaxial actuatorsare not depicted) are arranged. Other mechanisms are the same as in theembodiment of FIG. 9, and the measurement mount 15 is coupled to thebottom surface of the flange 18 by a kinematic support method, and thelaser interferometer system 12 or the like is fixed to the measurementmount 15.

In this example, the pattern of the reticle R is transferred and exposedonto the respective shot areas on the wafer W via the projection opticalsystem PLA by a step-and-scan method. At this time, the projectionoptical system PLA is suspended and supported from the intermediatemember 55, so in the same manner as in the first embodiment, thevibration isolation performance capability can be improved, and themechanism portion can be lightened.

In addition, in this example, the countermass 59 is arranged so as tocancel a reaction force generated when the reticle stage 60 is driven ata high speed (or acceleration) in the Y direction. At this time, if thecountermass 59 is simply arranged on the reticle base 57, there is apossibility that the countermass 59 which receives a reaction forcegenerates a vibration at a high frequency, which vibrates the reticlebase 57, and the measurement accuracy of the position of the reticlestage 60 may be deteriorated. In order to prevent this, in this example,as shown in FIG. 11, the countermass 59 (rigid structure) and the airpads 62A, 62B (rigid structure) are coupled via the flexure 63 (flexiblestructure), so the vibration generated by the countermass 59 is hardlytransmitted to the reticle base 57, and the position and the speed ofthe reticle stage 60 can be controlled with high accuracy.

In the same manner, as shown in FIG. 10, the intermediate member 55 andthe reticle base 57 (rigid structure) are coupled via the pivots 58A,58B (flexible structure), so the vibration of the reticle base 57 is nottransmitted to the measurement mount 56, which is provided with a laserinterferometer system. Thus, from this perspective as well, the positionand the speed of the reticle stage 60 can be controlled with highaccuracy.

In other words, in this example, flexible coupling is performed by theflexure 63 so that the moment by the vibration of the countermass 59 isnot transmitted to the reticle base 57, which is another structuralbody. Furthermore, flexible coupling is achieved by the pivots 58A, 58Bso that the moment by the vibration of the reticle base 57 is nottransmitted to the intermediate member 55 which is another structuralbody. Because of this, instead of the pivots 58A, 58B, a flexuremechanism also can be used. Support through this type of flexiblestructure also can be called “kinematic support” (includingsemi-kinematic support and pseudo-kinematic support for avoidance ofstress concentration and for vibration attenuation).

In this case, as shown in FIG. 10, for example, when the reticle base 57is vibrated, the position of the node of the first vibration mode is notdisplaced. Only the rotation moment is generated, and flexible couplingis achieved which allows rotation due to the pivots 58A, 58B. Therefore,virtually no vibration energy is transmitted to the intermediate member55 or to the measurement mount 56.

This type of structure is used, and the measurement mount 56 having alaser interferometer system which monitors the position of the reticlestage 60 is provided in the intermediate member 55 instead of in thereticle base 57. Therefore, for example, Abbe errors (errors determinedby the sine of a curved angle) due to the bow of the reticle base 57 canbe reduced. Furthermore, the projection optical system PLA is suspendedfrom the intermediate member 55, so flexible coupling is achieved in thehorizontal direction, which further shields vibration transmission.

Meanwhile, the vibration shielding effect is relatively small in thevertical direction (Z direction). Thus, ideally, a structure isdesirable in which the reticle base 57 is loaded on the vibrationisolation member, and its position is actively controlled. For thispurpose, for example, in FIG. 10, the reticle base 57 can be supportedvia three active type vibration isolation members on an undepictedcolumn. These active vibration isolation members include an air damperand an electromagnetic damper (such as a voice coil motor) whichgenerates a variable thrust in the Z direction. In this structure, withrespect to the three active vibration isolation members for the reticlebase 57, only three degrees-of-freedom (the position in the Z direction,pitching angle, and rolling angle) in the vertical direction can becontrolled with respect to the projection optical system PLA. Thecontrol band range is, for example, approximately 10 Hz.

If flexible coupling by this type of active vibration isolation memberis used, there is no relative interference of vibration energy,fluctuation load, and thermal displacement between the reticle base 57(reticle stage 60) and the projection optical system PLA. Furthermore,active relative positioning of the rigid structures is performed, sothere is no problem due to flexible coupling. In particular, in the caseof the scanning exposure apparatus of this example, if a function isprovided in which the reticle base 57 and the projection optical systemPLA are coupled by the above-mentioned flexible mechanism, andpositioning is actively performed with respect to each other, thesupport mechanism which supports the reticle base 57 and the projectionoptical system PLA does not need to have high rigidity, and thiscontributes to lightening of the device, temperature stability, andobtaining of a large space.

Furthermore, according to the embodiment of FIG. 10, the projectionoptical system PLA is suspended from the intermediate member 55 of theupper portion, so there is nothing that interferes with air flow fromthe center to the lower portion. Because of this, air conditioning ofthe device can be effectively performed by, for example, a downflowmethod. In addition, a large space is obtained, so the degree of freedomfor designing various sensors or the like arranged in the measurementmounts 15 and 56 can be increased. Furthermore, in the case of replacingthe projection optical system PLA, the projection optical system PLA canbe easily taken in and out by a method in which the projection opticalsystem PLA with the measurement mount 15 is removed from the rods52A-52C (coupling members) and passes through an undepicted gate-typecolumn. If this type of structure is used, the positioning relationshipsbetween the measurement system and the projection optical system PLA isadjusted in advance, and incorporation into the device is possibleas-is. Thus, assembly process reduction and cost reduction can beimproved.

Fifth Embodiment

The following explains a fifth embodiment of this invention withreference to FIGS. 12 and 13. In this example, that the projectionoptical system PL is supported from below by using a support mechanismthat has rods. In FIGS. 12 and 13, the same symbols are used for theportions corresponding to FIGS. 1-11, so a detailed explanation of thoseportions is omitted here. A flange 18 of the projection optical systemPL is mounted to a base molding 64 in which an opening is disposed. Thisbase molding 64 is supported by the support mechanism from a base plateBP. The support mechanism flexibly supports the projection opticalsystem PL in the Z direction via the base molding 64 and flexiblysupports the projection optical system PL in the horizontal direction(XY direction) as well. In this embodiment, the support mechanism isprovided with three rods 65 that are rigid in the Z direction andflexible in the horizontal direction (XY direction), flexures 66A, 66Bformed at both end portions of the rods 65, and a coupling portion thatconnects the base molding 64 with the upper side of flexure 66A.Furthermore, in this embodiment, the rods 65 and the flexure 66A areintegrally formed, but it is also acceptable to separate them using aleaf spring, etc. In addition, in this embodiment, the length of therods 65 is 1 m or longer.

With respect to the flexures 66A, 66B, in the same manner as theflexures 38Aa, 38Ab shown in FIG. 5, displacement in fivedegrees-of-freedom other than expansion in the Z direction is possible.Because of this, hardly any applied force acts between the base molding64 and the base plate BP. Thus, the base molding 64 is not easilydeformed by vibration, etc. from the base plate BP.

Furthermore, the support mechanism of this embodiment is provided with avibration isolation pad 67 arranged on the base plate BP, and thatsuppresses vibration in the Z direction transmitted from the base plateBP. For example, an air mount can be used as this vibration isolationpad 67.

Furthermore, in this embodiment, as shown in FIG. 13, the base molding64 is supported by three support mechanisms.

In addition, in this embodiment, as shown in FIG. 13, the reticle base57 is supported by four columns 33A-33D. Undepicted coils including avertical coil and a horizontal coil that constitute a stator of theactuator 54A is arranged between the columns 33A and 33C, opposite tothe base molding 64. In the same manner, undepicted coils including avertical coil and a horizontal coil that constitute a stator of theactuator 54B is arranged between the columns 33B and 33D, opposite tothe base molding 64. Permanent magnets that constitute movable elementsof the actuators 54A, 54B are arranged in the base molding 64.

The actuators 54A, 54B are constituted by three actuators that displacethe base molding 64 in the Z direction and three actuators that displacethe base molding in the circumferential direction. The actuators 54A,54B control the base molding 64 with six degrees-of-freedom.

If the projection optical system PL is supported by a parallel linkmechanism, the projection optical system PL is rigidly supported in theZ direction and the horizontal direction (XY direction). In contrast, asdescribed above, the support mechanism of this embodiment flexiblysupports the projection optical system PL in the Z direction and thehorizontal direction (XY direction), so the weight of the supportmechanism can be made light, and the vibration of the projection opticalsystem PL can be effectively cut off.

Furthermore, in this embodiment, the projection optical system PL issupported via the base molding 64, but the projection optical system PLcan be directly supported. In this case, the support mechanism can, forexample, directly support the projection optical system PL using theflange 18 of the projection optical system PL.

Furthermore, the projection optical system PL can be suspended fromabove using the support mechanism of this embodiment. In addition, inthe above-described embodiment, the projection optical system PL wassupported by using wires or rods, but the projection optical system canbe supported by using a chain. The exposure apparatus of this embodimentcan be applied to the above-mentioned stationary exposure type exposureapparatus, or to a scanning type exposure apparatus.

The projection exposure apparatus of the above-mentioned embodiments canbe manufactured by incorporating and optically adjusting an illuminationoptical system composed of a plurality of lenses and a projectionoptical system into the main body of the exposure apparatus, andinstalling the reticle stage and the wafer stage composed of a pluralityof mechanical parts to the main body of the exposure apparatus,connecting wires and pipes, and performing overall adjustment(electrical adjustment, operation check, etc.). Furthermore, it ispreferable that manufacturing of the projection exposure apparatus isperformed in a clean room with controlled temperature and cleanliness.

Furthermore, when a semiconductor device is manufactured by using theprojection exposure apparatus of the above-described embodiments, thesemiconductor device is manufactured by a step of designing aperformance capability and function of the device, a step ofmanufacturing a reticle based on the designing step, a step of forming awafer from a silicon material, a step of performing alignment by theexposure apparatus of the above-mentioned embodiment and exposing apattern of the reticle onto a wafer, a step of forming a circuit patternsuch as etching or the like, a step of assembling a device (including adicing process, a bonding process, a packaging process), a step oftesting, and the like.

This invention can be applied to a liquid crystal panel manufacturingexposure apparatus disclosed in, for example, International PublicationNo. WO 99/49504. Furthermore, this invention can be applied to aprojection exposure apparatus using extreme ultraviolet light (EUVlight) having a wavelength of several nm-100 nm as an exposure beam.

Furthermore, this invention is not limited to the application for theexposure apparatus for manufacturing a semiconductor device. Forexample, this invention can be applied to an exposure apparatus formanufacturing various devices such as a liquid crystal display elementformed on a square-shaped glass plate, or a display device such as aplasma display or the like, or an imaging element (CCD), amicro-machine, a thin-film magnetic head, a DNA chip, or the like.Furthermore, this invention can be applied to an exposure process(exposure apparatus) in which a mask (photomask, reticle, or the like)having a mask pattern of various devices is formed by using aphotolithographic process.

According to some aspects of this invention, when a projection opticalsystem as a rigid structure is suspended and supported with respect to apredetermined member as a rigid structure via a coupling member as aflexible structure, there is a possibility of using the advantages ofboth rigid and flexible structures. Therefore, compared to aconventional example, a ratio occupied by a rigid structure can bereduced, so without reducing a device performance capability, amechanism portion can be lightened, and the cost can be reduced.

The coupling members can extend through holes in the support member(flange 18) and attach to the lower surface of the flange 18, or can beattached inside of the flange 18, as opposed to being attached to thetop surface of the flange 18, as illustrated in the drawings.

While the invention has been described with reference to preferredembodiments thereof, which are exemplary, it is to be understood thatthe invention is not limited to the preferred embodiments orconstructions. The invention is intended to cover various modificationsand arrangements. In addition, while the various elements of thepreferred embodiments are shown in various combinations andconfigurations, that are exemplary, other combinations andconfigurations, including more, less or only a single element, are alsowithin the spirit and scope of the invention.

1. A projection optical device comprising: a projection optical systemwhich projects an image of a pattern; a support device having a flexiblestructure to support the projection optical system; and a positioningdevice having an actuator to position the projection optical system. 2.The projection optical device of claim 1, wherein the flexible structurehas a lower characteristic frequency in a direction perpendicular to anoptical axis of the projection optical system than in a directionparallel to the optical axis of the projection optical system.
 3. Theprojection optical device of claim 1, wherein the flexible structureincludes a wire.
 4. The projection optical device of claim 3, whereinthe flexible structure includes a flexure coupled to the wire.
 5. Theprojection optical device of claim 4, wherein the flexure is a spring.6. The projection optical device of claim 1, wherein a length of theflexible structure is at least 1 meter.
 7. The projection optical deviceof claim 1, wherein the flexible structure includes a rod member and aflexure provided on at least one end of the rod member.
 8. Theprojection optical device of claim 7, wherein the rod member has aflexure provided on both ends of the rod member.
 9. The projectionoptical device of claim 1, wherein the support device supports theprojection optical system from an upper side of the projection opticalsystem.
 10. The projection optical device of claim 1, wherein thesupport device supports the projection optical system from below theprojection optical system.
 11. The projection optical device of claim 1,further comprising a vibration isolation portion which reduces avibration in an optical axis direction of the projection optical system,the vibration isolation portion is provided at one end of the flexiblestructure.
 12. The projection optical device of claim 1, wherein thesupport device comprises a frame to which one end of the flexiblestructure is attached, such that the projection optical system hangsfrom the frame via the flexible structure.
 13. The projection opticaldevice of claim 12, wherein the actuator positions the projectionoptical system with respect to the frame in a non-contact manner. 14.The projection optical device of claim 13, wherein the positioningdevice comprises: a displacement sensor which measures sixdegrees-of-freedom of displacement information of the projection opticalsystem with respect to the frame.
 15. The projection optical device ofclaim 1, wherein the support device supports the projection opticalsystem via a flange portion fixed to a side surface of the projectionoptical system; and further comprising a measuring unit which iskinematically supported with respect to the flange portion and which isprovided with a sensor for measuring a positional relationship betweenthe projection optical system and a predetermined member.
 16. Theprojection optical device of claim 1, wherein a member in which thepattern is formed is integrally fixed to the projection optical system.17. The projection optical device of claim 16, further comprising amicro-moving mechanism which micro-moves the member in which the patternis formed with respect to the projection optical system.
 18. Theprojection optical device of claim 1, wherein the support devicecomprises a frame to which one end of the flexible structure isattached, such that the projection optical system hangs from the framevia the flexible structure; and further comprising: a base which issupported by the frame via a vibration isolation member; and a stagewhich drives a member in which the pattern is formed, on the base. 19.The projection optical device of claim 18, wherein the vibrationisolation member includes one of a pivot and a flexure.
 20. Theprojection optical device of claim 18, further comprising: a countermasswhich moves on the base so as to cancel a reaction force that isgenerated by movement of the stage; and a flexure which supports thecountermass on the base.
 21. The projection optical device of claim 1,wherein the projection optical system is arranged in a downflowenvironment.
 22. The projection optical device of claim 15, wherein themeasuring unit includes a laser interferometer, and further comprising alocal gas flow system which performs a local downflow of a gas withrespect to an optical path of a laser beam used by the laserinterferometer.
 23. The projection optical device of claim 1, furthercomprising: a tube which is arranged along a side surface of theprojection optical system; and a liquid supply which supplies a coolingliquid to the tube.
 24. An exposure apparatus provided with theprojection optical device of claim 1, wherein an image of the pattern istransferred and exposed onto a substrate by the projection opticalsystem.
 25. A projection optical device comprising: a projection opticalsystem which projects an image of a pattern; and a liquid supply whichsupplies a temperature-controlled liquid to a side surface of theprojection optical system utilizing gravity to cause thetemperature-controlled liquid to flow along the side surface of theprojection optical system.
 26. The projection optical device of claim25, wherein the liquid supply comprises: a tube which is wrapped aroundthe side surface of the projection optical system; and a liquidcirculation system which circulates the temperature-controlled liquidthrough the tube by a siphon principle.
 27. An exposure apparatusprovided with the projection optical device of claim 25, wherein animage of the pattern is transferred and exposed onto a substrate by theprojection optical system.
 28. The projection optical device of claim25, wherein the liquid supply comprises: a liquid reservoir locatedadjacent to a vertically upper portion of the projection optical system;the tube which is wrapped around the side surface of the projectionoptical system, the tube in communication with the liquid reservoir; anda liquid return path through which the fluid that has passed through thetube is returned to the liquid reservoir.
 29. The projection opticaldevice of claim 28, wherein the liquid return path includes atemperature control system that controls the temperature of the liquid,the temperature control system includes a pump that pumps the liquid tothe liquid reservoir.
 30. A method of controlling a temperature of aprojection optical system which projects an image of a pattern in aprojection optical device, the method comprising: supplying atemperature-controlled liquid to a side surface of the projectionoptical system utilizing gravity to cause the temperature-controlledliquid to flow along the side surface of the projection optical system.31. The method of claim 30, wherein: the temperature-controlled liquidis supplied through a tube which is wrapped around the side surface ofthe projection optical system in order to control the temperature of theprojection optical system; and further comprising: circulating thecooling liquid through the tube by a siphon principle.
 32. The method ofclaim 30, further comprising: providing a liquid reservoir locatedadjacent to a vertically upper portion of the projection optical system;supplying the temperature-controlled liquid to the tube which is wrappedaround the side surface of the projection optical system from the liquidreservoir; and returning the fluid that has passed through the tube tothe liquid reservoir by a liquid return path.
 33. The method of claim32, further comprising: controlling the temperature of the liquid in theliquid return path by using a temperature control system; and pumpingthe liquid through the liquid return path and into the liquid reservoirby using a pump.
 34. A method of supporting a projection optical systemwhich projects an image of a pattern in a projection optical device, themethod comprising: supporting the projection optical system by aflexible structure of a support device; and positioning the projectionoptical system by an actuator of a positioning device.
 35. The method ofclaim 34, wherein the flexible structure has a lower characteristicfrequency in a direction perpendicular to an optical axis of theprojection optical system than in a direction parallel to the opticalaxis of the projection optical system.
 36. The method of claim 34,wherein the flexible structure includes a wire.
 37. The method of claim36, wherein the flexible structure includes a flexure coupled to thewire.
 38. The method of claim 37, wherein the flexure is a spring. 39.The method of claim 34, wherein a length of the flexible structure is atleast 1 meter.
 40. The method of claim 34, wherein the flexiblestructure includes a rod member and a flexure provided on at least oneend of the rod member.
 41. The method of claim 40, wherein the rodmember has a flexure provided on both ends of the rod member.
 42. Themethod of claim 34, wherein the support device supports the projectionoptical system from an upper side of the projection optical system. 43.The method of claim 34, wherein the support device supports theprojection optical system from below the projection optical system. 44.The method of claim 34, further comprising: providing a vibrationisolation portion at one end of the flexible structure, the vibrationisolation portion reduces a vibration in an optical axis direction ofthe projection optical system.
 45. The method of claim 34, wherein thesupport device comprises a frame to which one end of the flexiblestructure is attached, such that the projection optical system hangsfrom the frame via the flexible structure.
 46. The method of claim 45,wherein the actuator positions the projection optical system withrespect to the frame in a non-contact manner.
 47. The method of claim46, wherein the actuator measures six degrees-of-freedom of displacementinformation of the projection optical system with respect to the frame.48. The method of claim 34, wherein the support device supports theprojection optical system via a flange portion fixed to a side surfaceof the projection optical system, and further comprising: providing ameasuring unit which is kinematically supported with respect to theflange portion and which includes a sensor for measuring a positionalrelationship between the projection optical system and a predeterminedmember.
 49. The method of claim 34, further comprising: providing amicro-moving mechanism which micro-moves a member in which the patternis formed with respect to the projection optical system.
 50. The methodof claim 34, wherein the support device comprises a frame to which oneend of the flexible structure is attached, such that the projectionoptical system hangs from the frame via the flexible structure; andfurther comprising: providing a base which is supported by the frame viaa vibration isolation member; and providing a stage which drives amember in which the pattern is formed, on the base.
 51. The method ofclaim 50, wherein the vibration isolation member includes one of a pivotand a flexure.
 52. The method of claim 50, further comprising: providinga countermass which moves on the base so as to cancel a reaction forcethat is generated by movement of the stage; and providing a flexurewhich supports the countermass on the base.
 53. The method of claim 34,further comprising: arranging the projection optical system in adownflow environment.
 54. The method of claim 48, wherein the measuringunit includes a laser interferometer, and further comprising: providinga local gas flow system which performs a local downflow of a gas withrespect to an optical path of a laser beam used by the laserinterferometer.
 55. The method of claim 34, further comprising:providing a tube which is arranged along a side surface of theprojection optical system; and providing a liquid supply which suppliesa cooling liquid to the tube.